1. Field of the Invention:
The present invention relates to an apparatus for feeding a scanned medium in an auxiliary scanning direction by gripping the scanned medium with a feed drum which is rotated and nip rollers associated with the feed drum.
2. Description of the Related Art
Recording apparatuses for recording images on scanned media have been widely used. In such recording apparatuses, a light beam emitted from a light beam generator is applied through a light beam deflector and a scanning lens to scan a scanned medium in a main scanning direction, and the scanned medium is fed in an auxiliary scanning direction by an auxiliary scanning feed mechanism for recording an image on or reading an image from the scanned medium.
The auxiliary scanning feed mechanism usually employs a rotating feed drum, and nip rollers movable toward and away from the feed drum, for feeding the scanned medium in the auxiliary scanning direction.
While the scanned medium is being held against an outer circumferential surface of the feed drum by the nip rollers, the scanned medium often tends to sag due to gravity or flexure thereof. When the scanned medium sags, it is floated or curved off the outer circumferential surface of the feed drum, resulting in a feed error being produced or, on occasion, the lines recorded on the scanned medium by the application of a light beam being unduly curved.
When color-separated films of four colors, i.e., cyan, magenta, yellow, and black (C, M, Y, BK) are to be produced using such an auxiliary scanning feed mechanism in a color platemaking process, if the films suffer respective feed errors caused by the auxiliary scanning feed mechanism, then respective images on the films are out of register with each other when superimposed, resulting in a reduction in register accuracy.
It has been the practice in the color platemaking process to place four color-separated images in one plate, sever the color-separated images after the plate has been produced, and use the color-separated images in superimposed relation to each other. In such a practice, it is important that a positional error (absolute positional error) of any individual dot on one film be in an allowable range.